These are instructions for making non-toxic invisible ink using baking soda (sodium bicarbonate).
Time Required: A Few Minutes
- There are at least two methods to use baking soda as an invisible ink. Mix equal parts water and baking soda.
- Use a cotton swab, toothpick, or paintbrush to write a message onto white paper, using the baking soda solution as 'ink'.
- Allow the ink to dry.
- One way to read the message is to hold the paper up to a heat source, such as a light bulb. The baking soda will cause the writing in the paper to turn brown.
- A second method to read the message is to paint over the paper with purple grape juice. The message will appear in a different color.
- If you are using the heating method, avoid igniting the paper - don't use a halogen bulb.
- Baking soda and grape juice react with each other in an acid-base reaction, producing a color change in the paper.
- The baking soda mixture can also be used more diluted, with one part baking soda to two parts water.
- Grape juice concentrate results in a more visible color change than regular grape juice.
What You Need:
- Baking Soda
- Light Bulb (heat source)
- Paintbrush or Swab
- Measuring Cup
- Purple Grape Juice (opt.)